We will study the central taste mechanisms of rats and the interaction of taste with learning and motivation. Electrophysiological and behavioral approaches are employed. First, as thalamic taste cells are studied through microelectrodes an analysis is made of their responses. It is hoped that stimuli which evoke excitatory responses and those which cause inhibition will fall into a pattern in the generated space, such as concentric circles. Next, a taste adaptation study examines neural responses to distilled water following adaptation to sapid solutions. Inhibitory thalamic responses to taste solutions are often followed by a rebound response to water. This experiment is designed to quantify that response. Then, in the pontine taste relay, the response characteristics of single neurons will be studied. Computer analysis will permit the generation of a pontine "taste space" involving the stimuli used. The interaction of taste with motivation and learning is examined in two behavioral experiments. First, the rate of self-stimulation is measured as appetitive solutions stimulate the tongue. Sensitivity to such stimuli among medial forebrain bundle neurons suggests the self-stimulation rate may be increased by their application. Secondly, multiunit neural responses, recorded from the thalamus both prior and subsequent to the establishment of a conditioned taste aversion, are studied to detect any response change which reflects the intervening experience. Next, rats will be raised with one predominant taste experience to see if this alters the sensitivity of their taste neurons. Finally, taste responses will be recorded from the pigeon thalamus to establish response characteristics and extend neural coding principles to lower animals.